Well, your list of plans certainly allows you to enjoy many of Switzerland's highlights. Whether it's doable depends on the number of days you intend to spend in each town. If you're able to allocate about 15 days for the entire trip, then yes, I'd say your route is certainly worthwhile. If on the other hand you'd choose to explore each location for no long than 1 or 2 nights, I'd personally feel it would all be too rushed. But that's a very personal decision. You'd best check traveling times with the aid of the timetable and decide what's acceptable to you and your fellow travelers (if any). If you don't mind long traveling times and switching hotels quite often, that's just fine of course. Here's what I'd prefer:

3-4 nights in Lucerne. It's a beautiful region with lots of options for scenic day trips. You can use the Wilhelm Tell Express route when traveling from Lugano to Lucerne via Flüelen. There's no need to use the official 1st class package. Regular trains (and, if you like, boats) will provide a similar experience;

3-4 nights in or near Lauterbrunnen. I think you've already explored the exensive range of day trip options in this region

Which pass is best depends on your finalized plans. If you roughly follow the advice above, I'd certainly recommend a 15 day Swiss Travel Pass. It's by far the easiest mode of traveling. All details, including purchase options and validity information, can be found at www.myswissalps.com/sw isstravelpass. Here's how to find out which pass suits your plans best.